Sediment collected near an aluminum plant in the massena area of the St. Lawrence River are lethal to larvae of the aquatic insect, Chironomus tentans. Initial studies suggest that concentration of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins (PCDD)s/polychlorinated dibenzofurans (PCDFs) in the sediment cannot account for the toxicity of the sediment. The major objective of this proposal is to determine the complete range of toxic compounds in the sediment using bioassays in conjunction with chemical fraction. This novel approach, termed bioassay-directed chemical analysis can greatly simplify the identification of toxic compounds in complex environmental samples. The task will be accomplished in three phases. In the first phase the sediment will be sequentially extracted with two solvents (toluene and methanol) of increasing polarity followed by extraction with water. The extracts will be subjected to a battery of one in vivo and four in vitro bioassays to determine acute toxicity, genotoxicity estrogenicity/antiestrogenicity and neurotoxicity. For the acute toxicity measurements we will use the Chironomus tentans larvae procedure used in our previous work and also a rapid bacterial assay based ont the ability of a toxicant to reduce light output from a luminescent bacterium. Genotoxicity will be assessed with a nonluminescent variant of the bacterium to which luminescence can be restored by a mutation. Estrogenicity/antiestrogenicity ad neurotoxicity will be evaluated by mammalian cell systems based on the growth of MCF-7 human breast cancer cells and catecholamine metabolism in rat brain slices respectively. The selected bioassays are simple and rapid and they cover a range of important biological responses which could produce adverse health effects in the human population. In the second phase the extracts will be subjected to chemical fractionation and the different fractions will be evaluated by the bioassays described above. Fractions showing an increase or decrease in toxicity relative to the extract from which they were derived will be analyzed for toxic compounds using state-art-instruments such as high and low resolution mass spectrometers and Fourier Transform infrared spectroscopy. In the final phase the bioaccumulation and/or metabolism of the toxic compounds will be determined by exposing fish to the sediment in the laboratory.